Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Hussain, P.S.

A novel machine-learning-based flavor-tagging algorithm combining same-side and opposite-side tagging is used to obtain the equivalent of 27 500 tagged (Formula presented) decays from (Formula presented) collisions at (Formula presented), collected by the CMS experiment and corresponding to an integrated luminosity of (Formula presented). A time- and flavor-dependent angular analysis of the (Formula presented) final state, consistent with a (Formula presented) decay, is used to measure parameters of the (Formula presented) system. The weak phase is measured to be (Formula presented), which, combined with the (Formula presented) CMS result, gives (Formula presented). This value differs from zero by 3.2 standard deviations, providing the first evidence for mixing-induced (Formula presented) violation in (Formula presented) decays. All measured physics parameters are found to agree with standard model predictions where available.

Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Dragicevic, M.; Giordano, C.; Hussain, P.S.

A search for the standard model Higgs boson decaying to a charm quark-antiquark pair, (Formula presented), produced in association with a top quark-antiquark pair ((Formula presented)) is presented. The search is performed with data from proton-proton collisions at (Formula presented), corresponding to an integrated luminosity of (Formula presented). Advanced machine learning techniques are employed for jet flavor identification and event classification. The Higgs boson decay to a bottom quark-antiquark pair is measured simultaneously and the observed (Formula presented) event rate relative to the standard model expectation is (Formula presented). The observed (expected) upper limit on the product of production cross section and branching fraction (Formula presented) is 0.11 (0.13) pb at 95% confidence level, corresponding to 7.8 (8.7) times the standard model prediction. When combined with the previous search for (Formula presented) via associated production with a (Formula presented) or (Formula presented) boson, the observed (expected) 95% confidence interval on the Higgs-charm Yukawa coupling modifier, (Formula presented), is (Formula presented) (2.7), the most stringent constraint to date.

Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Damanakis, K.; Dragicevic, M.

This Letter reports the first measurement of photonuclear (Formula presented) meson production in ultraperipheral heavy ion collisions. The study is performed using lead-lead collision data, with an integrated luminosity of (Formula presented), collected by the CMS experiment at a nucleon-nucleon center-of-mass energy of 5.36 TeV. Photonuclear events, where one of the colliding nuclei breaks up and the other remains intact, are selected based on breakup neutron emissions and by requiring no particle activity in a large rapidity interval in the direction of the photon-emitting nucleus. The (Formula presented) mesons are reconstructed via the (Formula presented) decay channel, with the cross section measured as a function of (Formula presented) meson transverse momentum and rapidity. The results are compared with next-to-leading-order perturbative QCD calculations that employ recent parametrizations of the lead nuclear parton distribution functions, as well as with predictions based on the color glass condensate framework. This measurement is the first photonuclear collision study characterizing parton distribution functions of lead nuclei for parton fractional momenta (Formula presented) (relative to the nucleon) ranging approximately from a few (Formula presented) to (Formula presented) for different hard energy scale (Formula presented) selections.

Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Dragicevic, M.; Giordano, C.; Hussain, P.S.

Using proton-proton collision data collected by the CMS experiment at (Formula presented) in 2016-2018, corresponding to an integrated luminosity of (Formula presented), the first full reconstruction of the three vector (Formula presented) meson states, (Formula presented), (Formula presented), and (Formula presented), is performed. The mass differences between the excited mesons and their corresponding ground states are measured to be (Formula presented), (Formula presented), and (Formula presented), where the first uncertainties are statistical and the second are systematic. These results improve on the precision of previous measurements by an order of magnitude.

Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Dragicevic, M.; Giordano, C.; Hussain, P.S.

The first observation of single top quark production in association with a (Formula presented) and a (Formula presented) boson in proton-proton collisions is reported. The analysis uses data at center-of-mass energies of 13 and 13.6 TeV recorded with the CMS detector at the CERN LHC, corresponding to a total integrated luminosity of (Formula presented). Events with three or four charged leptons, which can be electrons or muons, are selected. Advanced machine-learning algorithms and improved reconstruction methods, compared to an earlier analysis, result in an unprecedented sensitivity to (Formula presented) production. The measured cross sections for (Formula presented) production are (Formula presented) and (Formula presented) for (Formula presented) and 13.6 TeV, respectively. The signal is established with a statistical significance of 5.8 standard deviations, with 3.5 expected, compared to the background-only hypothesis.

Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Hussain, P.S.; Jeitler, M.

Nuclear medium effects on (Formula presented) meson production are studied using the binary-collision scaled cross section ratio between events of different charged-particle multiplicities from proton-lead collisions. Data, collected by the CMS experiment in 2016 at a nucleon-nucleon center-of-mass energy of (Formula presented), corresponding to an integrated luminosity of (Formula presented), were used. The scaling factors in the ratio are determined using a novel approach based on the (Formula presented) cross sections measured in the same events. The scaled ratio for (Formula presented) is consistent with unity for all event multiplicities, putting stringent constraints on nuclear modification for heavy flavor.

Hayrapetyan, A.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Bergauer, T.; Chatterjee, S.; Damanakis, K.; Dragicevic, M.; Hussain, P.S.; Jeitler, M.

A search is presented for an extended Higgs sector with two new particles, (Formula presented) and (Formula presented), in the process (Formula presented). Novel neural networks classify events with diphotons that are merged and determine the diphoton masses. The search uses LHC proton-proton collision data at (Formula presented) collected with the CMS detector, corresponding to an integrated luminosity of (Formula presented). No evidence of such resonances is seen. Upper limits are set on the production cross section for (Formula presented) between 300 and 3000 GeV and (Formula presented) between 0.5% and 2.5%, representing the most sensitive search in this channel.

Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Damanakis, K.; Dragicevic, M.; Giordano, C.

A measurement is presented of the cross section in proton-proton collisions for the production of two (Formula presented) bosons and one (Formula presented) boson. It is based on data recorded by the CMS experiment at the CERN LHC at center-of-mass energies (Formula presented) and 13.6 TeV, corresponding to an integrated luminosity of (Formula presented). Events with four charged leptons (electrons or muons) in the final state are selected. Both nonresonant (Formula presented) production and (Formula presented) production, with the Higgs boson decaying into two (Formula presented) bosons, are reported. For the first time, the two processes are measured separately in a simultaneous fit. Combining the two modes, signal strengths relative to the standard model (SM) predictions of (Formula presented) and (Formula presented) are measured for (Formula presented) and 13.6 TeV, respectively. The observed (expected) significance for the triboson signal is 3.8 (2.5) standard deviations for (Formula presented), thus providing the first evidence for triboson production at this center-of-mass energy. Combining the two modes and the two center-of-mass energies, the inclusive signal strength relative to the SM prediction is measured to be (Formula presented), with an observed (expected) significance of 4.5 (5.0) standard deviations.

Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Chatterjee, S.; Damanakis, K.

A search for the rare decay (Formula presented) is reported using proton-proton collision events at (Formula presented) collected by the CMS detector in 2022-2023, corresponding to an integrated luminosity of (Formula presented). This is the first analysis to use a newly developed inclusive dimuon trigger, expanding the scope of the CMS flavor physics program. The search uses (Formula presented) mesons obtained from (Formula presented) decays. No significant excess is observed. A limit on the branching fraction of (Formula presented) at 95% confidence level is set. This is the most stringent upper limit set on any flavor changing neutral current decay in the charm sector.

Chekhovsky, V.; Hayrapetyan, A.; Makarenko, V.; Tumasyan, A.; Adam, W.; Andrejkovic, J.W.; Benato, L.; Bergauer, T.; Chatterjee, S.; Damanakis, K.

Incoherent (Formula presented) photoproduction in heavy ion ultraperipheral collisions (UPCs) provides a sensitive probe of localized, fluctuating gluonic structures within heavy nuclei. This Letter reports the first measurement of the photon-nucleon center-of-mass energy ((Formula presented)) dependence of this process in PbPb UPCs at a nucleon-nucleon center-of-mass energy of 5.02 TeV, using (Formula presented) of data recorded by the CMS experiment. The measurement covers a wide (Formula presented) range of (Formula presented), probing gluons carrying a fraction (Formula presented) of nucleon momentum down to an unexplored regime of (Formula presented). Compared to baseline predictions neglecting nuclear effects, the measured cross sections exhibit significantly greater suppression at lower (Formula presented). Additionally, the ratio of incoherent to coherent photoproduction is found to be constant across the probed (Formula presented) and (Formula presented) range, disfavoring the establishment of the black disk limit. This Letter provides critical insights into the (Formula presented)-dependent evolution of fluctuating gluonic structures within nuclei and calls for further advancements in theoretical models incorporating nuclear shadowing and gluon saturation.